Fuse structures



June 7, 1960 F. J. KOZACKA FUSE STRUCTURES Filed April 15, 1959 IIIIIIIIIII United States Patent FUSE STRUCTURES Frederick J. Kozacka, South Hampton, N.H., assignor to The Chase-Shawmut Company, Newburyport, Mass.

' Filed Apr. 15, 1959, Ser. No. 806,564 s Claims. (Cl. 200-131 This. application is a continuation-in-part of my copending patent application Ser. No. 775,881, filed Nov. 24, 1958, for Fuse Structures.

The present invention has reference to electric fuses for the protectiono'f electric circuits, electric machinery and electric apparatus, and more particularly to electric fuses having blade' contacts for inserting the fuses into a fuse. holder.

It is a general object of this invention to provide fuses of improved design.

Another object of this invention is to provide a simple structure for maintaining the blade contacts in position, or supporting the blade contacts, and for maintaining the terminal caps or ferrules in position, which structure is inherently resilient and is not adversely affected by changes in ambient temperature.

Some of the simplest prior art structures for supporting blade contacts of electric fuses include transverse pins on which the blade contacts are mounted. To preclude movement of the blade contacts relative to the supporting pins the latter have either been serrated, or expanded to both sides of the blade contacts. Both methods of mounting blade contacts on pins involve relatively complex and expensive operations and do not compensate for dimensional changes resulting from changes in ambient temperature.

It is, therefore, another object of the invention to provide electric fuses including pin-mounted blade contacts whose manufacture does not call for such expensive operations as' mounting a blade contact having a hole drilled to a close tolerance on a serrated pin, or expanding a hollow pin supporting a blade contact to maintain the blade contact in position, and which fuses are not adversely affected by changes in ambient temperature.

Another object of this invention is to provide electric fuses having terminal caps or ferrules which are held in place by simple resilient means not affected by changes in ambient temperature.

These and other objects of the invention and advantages thereof will become more apparent from the following description of preferred embodiments of the invention when taken in connection with the accompanying drawings, wherein 1 Fig.1 is a longitudinal section on a large scale of an electric fuse embodying the invention taken along 1-! of Fig. 2, the middle portion of the fuse being broken away;

Fig. 2 is a section along 2-2 of Fig. 1 and shows one portion of the fuse completely assembled and anotherportion of the fuse not completely assembled, the middle portion of the fuse being broken away as in Fig. 1;

Fig. 3 is a portion of Fig. 2 drawn on a larger scale; and

Fig. 4 is an isometric exploded view of another embodiment of the invention.

Referring now to the drawing, and more particularly to Figs. 1-3 thereof, numeral 1 has been applied to indicate a tubular casing of insulating material such as, for instance, vulcanized fiber. A pair of knife blade contacts 2 extends in a direction longitudinally of casing 1 and is inserted into the axially outer ends thereof. Blade contacts 2 may be made of solid copper and are conductively interconnected by a pair of fusible elements or fuse links 3 in form of copper or silver ribbons. Casing 1 is filled with a pulverulent arc-quenching filler 13 and the ends of easing 1 are closed by washers or discs 14 of asbestos or a like material of which each has a rectangular cutout portion for the passage of one of blade contacts 2. Reference numeral 4 has been applied to indicate spot welds conductively interconnecting fusible elements 3 with the blade contact 2 on the right end of casing 1 and the blade contact 2 on the left end of casing 1. The fusible elements or fuse links 3 may have points of reduced cross-section (not shown) to establish multibreaks when interrupting an electric circuit, as generally known in the art. Each of the blade contacts 2 is provided with a circular transverse perforation 5 adjacent the axially inner end thereof. The fuse structure comprises a pair of hollow cylindrical springs in the shape of pins to which numeral 6 has been applied. Each pin 6 is made of rolled sheet material wound to form a substantially cylindrical surface, defining a slot 6a extending in a direction longitudinally thereof, and each pin 6 has chamfered ends. Pins 6 have a predetermined outer diameter and each projects through holes or bores 7 in casing 1 transversely through casing 1 and also through the perforation 5 in one of blade contacts 2. The perforations 5 are drilled to rough tolerances and have a diameter less than the outer diameter of pins 6. Each of pins 6 is elastically compressed in the center region thereof by one of blade contacts 2. Thus each pin 6 supports resiliently one of blade contacts 2, and the latter are firmly held in position irrespective of whether or not the diameter of the perforations 5 increases due to a high ambient temperature. Reference numeral 8 indicates a pair of metal caps each mounted on an axially outer end of casing 1. Caps 8 close casing 1 and have rectangular punched-out portions definiiji passages 9 for each of blade contacts 2. Each cap 8 has two indentations 10 driven into the axially outer ends of one of pins 6, elastically expanding the axially outer ends thereof and increasing the diameter thereof beyond their normal diameter when not subjected to any elastic stress. Thus the diameter of pins 6 is decreased in the center region thereof by blade contacts 2 and increased at the axially outer ends thereof by indentations 10. The longitudinal slot 6a in pins 6 is narrowed in the center region thereof and widened at the axially outer ends thereof. The cup-shaped indentations 10 of caps 8 are firmly but resiliently held in position by the expanded and outwardly flaring ends of pins 6. This kind of connection does not tend to become loose even if the indentations 10 contract on account of a relatively low ambient temperature.

The right side of Fig. 2 shows the fuse structure in the process of being assembled, the terminal cap 8 having been mounted on casing 1, but no indentations 10 having yet been formed in cap 8 and driven into casing 1 and into hollow pin 6. The left side of Fig. 2 and Fig. 3

- show a cap 8 firmly and resiliently held in position by indentations 10 driven into pin 6.

In the modification of the invention shown in Fig. 4 like parts as in Figs. 1-3 have been indicated by like reference numerals with a prime sign added to them. Thus 2' indicates a blade contact inserted into casing 1' and provided with a transverse perforation 5'. Pin or spring 6' is longitudinally slotted at 6a and intended to be inserted into openings 7 and casing 1 and pushed through circular perforation 5 in blade contact 2'. Cap 8 is provided with two diametrically opposite holes 11' intended to be arranged in registry with the holes 7' in casing 1', and with the axially outer ends of pin 6'. When cap 8' is mounted on casing 1', blade contact 2' projects axially outwardly through the rectangular opening 9 in cap 8. Thesizeof holes 5 in blade contact 2' is such as to compress the center portion of spring or pin 6 in the same wayas illustrated in the embodiment of the invention'shown injFigs. l-3. When spring or pin 6 is in position supporting blade contact 2' and resting with the axially outer .ends thereof in holes 7' in casing 1, the two drive screws 12' are being driven through holes 11' in cap 8' into the axially outer endsof spring or'pin 6'. This causes the axially outer ends of pin 6 to expand in the same fashion as shown in Figs. 1-3, thus firmly yet resiliently holding drivescrews 12, and hence also cap 8', in, position. 7 7

It will be apparent from the foregoing that the indentations 10 ofthe structure of Figs. 1-3, inclusive, and the drive screws 12 of the structure of Fig. 4 serve the same purpose. They are both plug means driven into the axially outer ends of the pins elastically expanding said axially outer ends and increasing the diameter thereof beyond their normal diameter.

While I have described what are at present considered to be preferred embodiments of the invention, it will be understood that various modifications may be made therein without departing from the spirit and scope of the invention as defined in the following claims.

I claim as my invention:

1. In an electric fuse in combination with a fusible element a tubular insulating casing housing said element; a pair of caps each mounted on an axially outer end of said casing and closing said casing; a pair of blade con-' tacts each projecting across one of said pair of caps into said casing, each conductively connected to one end of said element and each having a transverse circular perforation adjacent the axially inner end thereof; a pair of pinshaped springs formed of wound sheet material each adapted to be radially elastically compressed and to be radially elastically expanded at longitudinally spaced points thereof; each of said pair of springs having a predetermined diameter, each projecting transversely across said casing and through said perforation in one of said pair of blade contacts and each being elastically compressed in the center region thereof b'fi'one of said pair of blade contacts to a smaller diameter than said predetermined diameter; and plug means driven into the tudinally of said casing, inserted into said casing at the axially outer ends thereof, conductively interconnected by said element and each having a transverse circular perforation adjacent the axially inner end thereof; a pair of pin-shaped springs formed of wound sheet material each adapted to be radially elastically compressed and to be radially elastically expanded -at longitudinally spaced points thereof, each of said pai'r of springs having a predetermined diameter, each projecting transversely across said casing through said perforation in one of said pair of blade contacts and each being elastically compressed in the center region thereof by one of said pairof blade contacts to a smaller diameter .than said predetermined diameter; and a. pair of metal capseach mounted on an axially outer end of said casing, closing said casing and defining a passage for one of said pair of blade contacts, each of said pair of caps having a pair ofindentations driven into the axially outer endsof eachof said pair of springs elastically expanding said axially outer ends and increasing the diameter thereof beyond said predetermined diameter.

3. In an electric fuse in combination with a fusible element a tubular insulating casing housing said element, a pair of blade contacts extending in a direction longitudinally of said casing, inserted into'said casing at the axially outer ends thereof, conductively interconnected by said element and each having a transverse perforation adjacent the axially inner end thereof; 'a'pai'r. of pin-shaped springs formed of wound sheet material each adapted to be radially elastically compressed and to be radially elastically expanded. at longitudinally spaced points thereof,

each of said pair of springs having a predetermined diameter, each projecting transversely across said casing through said perforation in oneof said pair of blade concasing, closing said casing and defining a passage for one axially outer ends of each of said pair of springs elasof said pair of blade contacts, each of said pair ofcaps having a pair of holes in registry with the axially outer ends of one of said pair ofspring's;and.a pair of drive screws projecting through said pair of'holes in each or said pair of caps into saidaxially outer ends of each of said pair of springs elastically expanding said axially outer ends and increasing the diameter thereof.

References'Cited in the file of this patent V UNITED STATES PATENTS 1,107,861 Stout Aug. 18, 1914' 1,237,211 'Leveen Aug. 14, 1917 2,665,348 Kozacka Jan. 5, 1954 2,864,916 3 Barrett et a1. Dec. 16, 1953 

